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TitleThe geochemical effects of olivine slurry replenishment and dolostone assimilation in the plumbing system of the Franklin Large Igneous Province, Victoria Island, Arctic Canada
AuthorHayes, B; Lissenberg, C J; Bédard, J H; Beard, C
SourceContributions To Mineralogy and Petrology vol. 169, no. 22, 2015 p. 1-18, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20140231
PublisherSpringer Nature
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories; Nunavut
NTS77E/04; 77E/05; 77E/12; 77E/13; 77F; 77G; 77H/04; 77H/05; 77H/12; 77H/13; 78A/04; 78A/05; 78A/12; 78A/13; 78B; 87E; 87F; 87G; 87H; 88A; 88B/01; 88B/02; 88B/03; 88B/04; 88B/05; 88B/06; 88B/07; 88B/08; 88B/09; 88B/10; 88B/11; 88B/15; 88B/16
AreaVictoria Island
Lat/Long WENS-120.0000 -107.0000 73.5000 70.0000
Subjectsgeochemistry; igneous and metamorphic petrology; regional geology; sills; dykes; mafic intrusive rocks; basalts; olivine; fractional crystallization; crystal fractionation; magma differentiation; cumulus processes; whole rock geochemistry; partial melting; mineral enrichment; Franklin LIP
Illustrationslocation maps; photographs; aerial photographs; schematic diagrams; photomicrographs; graphs; tables
ProgramGEM: Geo-mapping for Energy and Minerals PGE/Base Metals - Victoria Island (NWT and Nunavut)
Released2015 02 13
AbstractThe Neoproterozoic (~723 - 716 Ma) Franklin Large Igneous Province exposed on Victoria Island in the Canadian Arctic is comprised of a sill-dominated magma plumbing system overlain by the coeval Natkusiak flood basalts. We have investigated three sections, separated by a total of >50 km of distance, of a sill (the Fort Collinson Sill Complex) emplaced just above a prominent sedimentary marker unit. The sill is characterized by a basal olivine-enriched layer (OZ: up to 55 % olivine) and an upper gabbroic unit. The observed diversity of olivine compositions in the OZ implies that bulk-rock MgO versus FeO arrays reflect accumulation of a heterogeneous olivine crystal cargo. We suggest that the OZ was formed as a late olivine slurry replenishment in a partially crystallized gabbroic sill, propagating for over 50 km along strike. This interpretation is consistent with Pb-isotope data, which show that at least three geochemically distinct magmas were emplaced into the Fort Collinson Sill Complex. The OZs exhibit a gradual westward evolution toward more Fe-rich bulk compositions. This is best explained by progressive mixing of the replenishing olivine slurry with a resident gabbroic mush during westward flow. Pb-isotopic signatures suggest that magmas near the inferred conduit feeder assimilated small amounts (<10 %) of dolostone country rock, which may have locally buffered olivine compositions to high-Fo contents.
Summary(Plain Language Summary, not published)
Major element modeling implies that an olivine-rich replenishment progressively mixed with host gabbro as it propagated downstream in a sill.

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